Card Range To Study

29 Cards in this Set

•! Actinomyces!
•! Nocardia!
•! Dermatophilus!
•! Streptobacillus!
Note: These
organisms are linked
only by the fact that
they form ﬁlamentous
growths in vivo.!
Genetically distinct.!

Are Actinomyces gram+/-?

Gram +

Are Actinomyces aerobic or anaerobic?

What tissue are they adapted to?

Anaerobic.

Actinomyces spp. are highly adapted to _mucosal_
surfaces- do not commonly produce disease unless they
transgress the mucosal barrier and are deposited under
conditions of low oxygen tension!

Is Actinomyces endogenous or exogenous? Is it contagious?

No evidence of protective immunity, animal to animal
transmission does not occur.! This is an endogenous infection.

How does Actinomyces establish infections?

Establish infections by means of traumatic entry to an otherwise _sterile_ site. This site becomes anaerobic and the bacterium can grow.

What are the channels that Actinomyces create when they get established?

Once established they can proceed through tissues by means of
histolytic enzymes that allow the organism to extend without
regard to anatomical boundaries. Form __sinus tracts_- channels of
dead tissues that contain pus and often open to the surface.!

cervicofacial- common with poor oral hygiene -
periodontal disease- and tooth extraction. Lesions in the
jaw give the face a swollen, indurated appearance.!

What does thoracic actinomyces result in?

What is it associated with?

Thoracic- disease in the lungs. abscess formation can
occur. Often associated with _aspiration__ of a lung- oral
bacteria establish residence in the normally sterile site.

What does abdominal actinomyces result in?

Abdominal- surgery or trauma in the __bowel__. Also from
diverticulitis. Can eventually involve every organ
system.!

What does pelvic actinomyces result in?

Pelvic- 2° manifestation of abdominal actinomycoses, or
primary in the case of an intrauterine device. Can be a
simple vaginosis (note: no crossing of mucosal membrane)
but also can involve more serious destruction- including
tuboovarian abscesses and uretal obstruction. !

Antibiotics: high doses of penicillin may be required for
long periods. !
May also require surgical debridement.!

How do foxtail awns relate to actinomyces infections?

When dog owners talk about "foxtails," they
are actually speaking of the seed portion of
the foxtail grass. Once foxtail grasses dry
out, the seed detaches easily and sticks
readily to clothing and fur. Foxtail seeds can
enter a dog's body in a variety of ways and
once they enter, they are like a ﬁsh hook:
The seed only wants to move forward, not
backward. It's most common for a foxtail
seed to enter a dog's body through the skin,
nose, ears, paws, and eyes. Cases have even
been reported of foxtails being lodged in
male dogs' urethras. One vet mentioned
how a foxtail seed found in a dog's lung
was believed to have entered initially
through the dog's paw! Foxtail seeds are
tenacious!

Certain species of actinomyces use these plants
to traverse within the body- then cause purulent
disease.!

Bovine nocardial mastitis- usually associated
with poor hygiene/milking practices. Pathogen is
directly introduced into teat canal with
contaminated instruments or ﬂuids. Chronic, !
granulomatous- can lead to sinus tracts. !
Can be fatal via trauma (rupture of udder) or
during acute dissemination.!
If disseminated: causes suppurative,
granulomatous lesions.!
Unless caught early, antibiotics may not be
successful.!
Bovine Farcy- limited to tropics. Systemic
suppurative infections that trafﬁc through
lymphatics. N. farcinus!

What other organism does Actinomyces look like in gram stains?

Nocardia

Both gram +

What is dermatophils congolensis?

What is key to the infection?

Actinomyces

highly infectious organism- infects many species.
Aerobic, causes disease of dermal surfaces. Often insect-borne. Worldwide, but more problematic in tropics.
-Attacks areas of damaged skin- _moisture_ is
key.
-Back and pasterns: most common areas of infection in horses. Lesions are found on head, neck or back. Rain scald or rain rot: (figure 37.4)
-Lumpy wool, strawberry footrot: sheep
-In general- diseases manifest as a chronic __exudative dermatitis__ with scab formation.
-Infection is confined to the dermal layers- in moist environs, and the infection causes exudation that feeds the system.

What happens if dermaphilosis is left untreated?

how can you treat this disease?

Do insects serve as a resevoir for the pathogen?

If left untreated, a mud fever infection will spread up the legs.
The legs will swell and be intensely sore. The horse may
become lame. Infections in other areas will cause inflammation,
soreness and hair loss, severe infections may abcess.
Bacteria removed with antiseptics. Beta lactams also can be
used.
Best way to treat is to keep damaged areas dry- systemic
antibiotics can work- but keep animals dry if possible.
Address biting insect issues.
Do the insects serve as reservoir (as opposed to simply a
vector) for pathogen? Not known. Organism likely grows in
soil.

Does dermatophilosis cause microcolonies?

In what species does in occur?

Actinomyces

Organisms will form ﬁlaments in vivo- individual organisms can break off and start new microcolonies.